gentoo-overlay/app-misc/tracker/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
  <maintainer type="project">
    <email>gnome@gentoo.org</email>
    <name>Gentoo GNOME Desktop</name>
  </maintainer>
  <use>
    <flag name="miners">Install the <pkg>app-misc/tracker-miners</pkg> package for actual data mining support for tracker</flag>
    <flag name="stemmer">Add word stemming via <pkg>dev-libs/snowball-stemmer</pkg>.</flag>
  </use>
</pkgmetadata>